hwmon: (pwm-fan) Disable PWM if fetching cooling data fails

In case pwm_fan_of_get_cooling_data() fails we should disable the PWM
just like in the other error cases.

Fixes: 2e5219c7 ("hwmon: (pwm-fan) Read PWM FAN configuration from device tree")
Cc: <stable@vger.kernel.org> # 4.14+
Reported-by: Guenter Rock <linux@roeck-us.net>
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>